The present invention relates to a friction clutch for a land vehicle.
Generally, in a friction clutch for a vehicle, a friction facing of a clutch disc is pressed onto a flywheel by a pressure plate which is forced by a spring or springs. However, in this structure, when the facing wears,
the spring can not apply a sufficient force to the pressure plate, and thus, durability of the clutch is low.
As a counter measure, the applicant has already proposed, in the U.S. Pat. No. 4,479,570 (Japanese Patent Application Nos. 56-80455 and 56-82227), a pneumatic clutch in which a pressure plate is operated by a pneumatic cylinder. In this structure, the pressure plate can press the facing onto the flywheel by a constant force even when the facing wears. However, since the pneumatic cylinder is constructed to rotate together with a clutch cover, it is necessary to disposed a rotary joint having a complicated structure between a stationary air passage at the outside of the clutch cover and a rotating air passage at the inside of the cover.
Accordingly, it is an object of the invention to provide a friction clutch having high durability and including a joint of a simple structure.
Other object of the invention is to provide a friction clutch overcoming following disadvantages.
That is; either in a clutch of a spring type or a pneumatic type, the large clutch cover, which rotates together with the flywheel and the pressure plate, is required to support a spring or a pneumatic cylinder. Therefore, the whole structures become large.
Further, when the facing is pressed by the pressure plate onto the flywheel, which is provided at an end of an output shaft of an engine, the pressing force is applied through the flywheel to the output shaft, so that the bearing for the output shaft is liable to wear.
According to the invention, a friction clutch operated by a fluid pressure comprises an axially unmovable input shaft; a flywheel fixed to the input shaft; a clutch disc opposed to a friction surface of the flywheel; an output shaft connected to the clutch disc and disposed coaxially to the input shaft; a pressure plate for pressing a friction facing of the clutch disc onto the flywheel; a forcing mechanism of a fluid pressure type for forcing and moving the pressure plate through a bearing toward the flywheel; a forcing mechanism of a fluid pressure type for forcing the flywheel toward the clutch disc through a bearing;
stationary members to which the forcing mechanisms are fixed; and a pressure controlling mechanism for changing the pressures for both forcing mechanisms correspondingly to each other.
According to the above structure, the forcing mechanism of the fluid pressure type applies a constant force to the pressure plate, even when the facing wears, so that the pressure plate presses the facing onto the flywheel by a sufficient force.
Further, since the forcing mechanisms are mounted on stationary members, the pressure passages for the forcing mechanisms do not include a part which rotates. Therefore, it is not necessary to provide a rotary joint at the pressure passages.
Moreover, since the forcing mechanisms are disposed on the stationary member, a conventional clutch cover is not necessary. Therefore, the structure can be compact. In other words, since the bearings are associated to the forcing mechanisms, the forcing mechanisms can be mounted on the stationary member, and the conventional clutch cover can be eliminated.
Further, one of the forcing mechanisms forces the pressure plate toward the flywheel, while the other forces the flywheel toward the clutch cover, so that the pressing forces by both forcing mechanisms cancel each other. Therefore, a thrust is not applied through the flywheel to the input shaft, i.e., output shaft of the engine, and thus wear of a bearing mechanism (e.g., side metal) for the input shaft is prevented.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the Invention.